Modern consumer and industrial electronic devices require storage of information, such as digital photographs, electronic mail, calendar, or contacts. These devices can be electronic systems, such as notebook computers, desktop computers, servers, televisions, and projectors, and are providing increasing levels of functionality to support modern life. Preserving the user data stored in the storage devices is of the utmost importance.
Different approaches have been used to monitor the general condition of the stored data. With increasing areal density trade-offs are increasingly difficult and challenging to make. The primary purpose, of course, is to maintain high level of signal to noise ratio (SNR) for a given design with ever shrinking track pitch and the ability to stay on-track without increasing servo wedge overhead. In principle, the higher the track per inch (TPI) density, the harder it is to stay on-track without increasing the number of servo wedges, which increases the incidence of servo positional error signal (PES) related write aborts and potential adjacent track writes/corruptions.
A conventional defense to combat this type of data loss is to make the write unsafe (WUS) limit, which is used to abort a write, as small as possible without severely degrading write performance. With ever increasing TPI this capability can only shrink. Furthermore, similar condition can be created even without write abort. As long as there are small off-track writes (still within WUS limit), the adjacent track will likely be compromised.